The instant patent application describes a hydrogen storage unit useful for a hydrogen-based economy. The storage unit allows for fast and efficient cooling and/or heating thereof using gaseous hydrogen as a direct, convective heat transfer medium. The unit maximizes the cooling efficiency of the storage material therein while providing for a high packing density of the storage materials and ease of expansion of storage capacity by merely adding more storage material plates. The instant storage unit is useful in a hydrogen-based economy.
An infrastructure for such a hydrogen-based economy is disclosed in U.S. application Ser. No. 09/444,810, entitled "A Hydrogen-based Ecosystem" filed on Nov. 22, 1999 for Ovshinsky, et al. (the '810 application), which is hereby incorporated by reference. This infrastructure, in turn, is made possible by hydrogen storage alloys that have surmounted the chemical, physical, electronic and catalytic barriers that have heretofore been considered insoluble. These alloys are fully described in copending U.S. patent application Ser. No. 09/435,497, entitled "High Storage Capacity Alloys Enabling a Hydrogen-based Ecosystem", filed on Nov. 6, 1999 for Ovshinsky et al. (the '497 application), which is hereby incorporated by reference.
Hydrogen storage units have a number of requirements. First and foremost, they are required to be able to store hydrogen. This bare minimal requirement is met by many prior art storage units. However, to be commercially useful in a hydrogen-based economy, the hydrogen storage unit requires many more properties. One requirement is a high specific capacity hydrogen storage material. Such materials were invented by the instant inventors and are disclosed in the '497 application. Another requirement is a unit which has a high volumetric and gravimetric packing density of storage materials. One such unit is also disclosed in the '497 application.
A further requirement is a unit that has the ability to be cooled a high rate. This is required to be able to quickly charge hydrogen into the unit while maintaining proper operating temperature by removing the heat of hydride formation. The instant inventors have determined that maximal cooling using minimal hardware can be achieved using excess hydrogen flow though the system to remove the heat. A system which employs hydrogen cooling is also disclosed in the '497 application. However, such a unit also requires high cooling efficiency. To achieve this maximal efficiency, the temperature between the cooling hydrogen and the heated storage materials must be maximized, while maintaining the storage material at its proper operating temperature. This requires that the temperature rise of the cooling hydrogen over the entire length of contact between the hydrogen and the storage material be minimal. Prior hydrogen-cooled units fail to achieve this goal.
In addition to being able to quickly and efficiently cool the hydrogen storage materials within the storage unit, the hydrogen storage materials must be heated quickly and efficiently to release hydrogen therefrom during use. To accomplish this, there must be efficient thermal transfer from the source thereof through the bulk of the storage material. While most systems will transfer this heat, they do not do so efficiently.
Finally, for many applications ease of capacity expansion is a must. While many prior art systems do not allow for expansion, some do. However, with most systems, expansion of the amount of hydrogen storage materials reduces the cooling and heating efficiency.
Therefor, what is needed in the art is a high capacity hydrogen storage unit having high volumetric and gravimetric storage capacity (i.e., high packing density of storage materials), which is capable if being cooled at a high rate with maximal efficiency, is capable of efficient heat transfer from an internal heat source throughout the storage material, and is expandable without losing any of the aforementioned properties.